Proportional distribution of predominant rumen bacteria between the solid and the liquid portions of ruminal ingesta

Abstract

That certain bacteria in the rumen of sheep and cattle are attached to solid particles in the ruminal ingesta has been known for many years. In 1942 Baker published direct microscopical evidence that bacteria were attached to cellulose food particles and to starch granules in the rumen. The sites of attachment of these bacteria corresponded to sites of disintegration of the particles when viewed by polarised light. This indicated that at least bacteria attacking solid substrates such as cellulose and starch were attached to particles of ruminal ingesta. Van der Wath (1942) found rumen bacteria attached to particles of chemically pure cellulose and of crushed maize which he suspended in separate compartments of a pure silk bag inside the rumen of sheep. The bacteria associated with the particles of cellulose were mainly Gram negative rods , while clusters of iodophilic cocci were observed in most instances around the maize kernels . The latter organisms were isolated in pure culture and found to be heat-tolerant, short-chain, Gram positive cocci fermenting glucose, maltose, and other soluble sugars as well as starch. It was thus not surprising that many years later Schwartz et al (1964) obtained evidence which suggested that bacteria metabolising soluble substrates such as glucose also showed marked attachment to solid particles of ingesta.